Modern agriculture, including silviculture, often requires the planting of large numbers of substantially identical plants genetically tailored to grow optimally in a particular locale or to possess certain other desirable traits. Production of new plants by sexual reproduction, which yields botanic seeds, can be time- and labor-intensive and is often subject to genetic recombinational events resulting in variable traits in the progeny. Further, inbred strains such as those used to perform such crosses often lack vigor, resulting in low seed productivity.
In vitro culture of somatic or zygotic plant embryos can be used to produce large numbers of genetically identical embryos that have the capacity to develop into normal plants. However, the resulting embryos lack the protective and nutritive structures found in natural botanic seeds that shelter the plant embryo inside the seed from the harsh soil environment and nurture the embryo during the critical stages of sowing and germination. As a result, the embryos must usually be further cultured in vitro until they reach a "seedling" state characterized by the ability to photosynthesize, resist desiccation, produce roots able to penetrate soil, and fend off soil microorganisms. As used herein, the terms "Artificial" or "manufactured" seeds refer to seeds in which individual plant somatic or zygotic embryos are encapsulated in a hydrated gel. In the most advanced designs, the manufactured seed includes various protective and nutritive features that more closely mimic analogous structures of natural botanic seed.
There is a need for an improved manufactured seed that more closely mimics the function of natural, botanic seed by protecting the embryo against mechanical damage, desiccation, and attack by pathogens, herbivores, and pests, and promoting a high rate of germination. The present invention meets these and other needs.